1. Field of the Disclosure
This disclosure relates to the field of downhole tools associated with rotary drilling in earth formations, especially to reduction of damage and wear due to mechanical shock and vibration.
2. Description of the Related Art
Rotary drilling in earth formations is used to form boreholes for obtaining materials in the formations, such as hydrocarbons. Rotary drilling involves a drill bit disposed on a drilling end of a drill string that extends from the surface. The drill string is made up of a series of tubulars that are configured to allow fluid to flow between the surface and earth formation. Above and proximate to the drill bit may be formation and/or borehole measurement tools for measurement-while-drilling. Multiple tools may be grouped together as a bottom hole assembly.
During rotation of the drill bit, downhole tools in the bottom hole assembly may be subjected to vibrations and mechanical shocks that can damage the measurement tools, communication along the drill string, or connections between downhole tools and other downhole components. The electronic and mechanical devices in tools may be particularly sensitive to mechanical shock and vibration. Damage to electronics in downhole tools may reduce reliability and life of the tool. Failure of the tool can result in costly downtime due to halted drilling operations and tool repairs before drilling may resume. To reduce damage, and thus failures due to mechanical shock and vibration, the tools may be isolated from mechanical shocks by one or more shock absorbing devices, commonly called snubbers.
A snubber is generally a component configured to reduce tool damage and wear due to stresses caused by mechanical shock and vibration. Conventional snubbers reduce the mechanical shocks being transmitted along the longitudinal axis of a drill string from the direction of the drill bit through compressibility of the snubber material. The conventional snubber may be spring or elastomeric ring configured to compress longitudinally when exposed to mechanical shocks. The shock absorbing ability of the snubber is often a function the thickness and type of snubbing material. As such, snubbers are typically disposed on the side of a downhole tool where mechanical shocks are most likely to be generated.
There is a need for a durable snubber that reduces mechanical shocks to downhole tools. There is a need for a snubber that provides protection against shocks in radial and/or rotational directions as well as the longitudinal direction. There is also a need for a snubber that provides different degrees of protection along different degrees of freedom of the downhole tool.